/*
Given a m x n matrix, if an element is 0, set its entire row and column to 0. Do it in place.

click to show follow up.

Follow up:
Did you use extra space?
A straight forward solution using O(mn) space is probably a bad idea.
A simple improvement uses O(m + n) space, but still not the best solution.
Could you devise a constant space solution?
*/

class Solution {
public:
    void setZeroes(vector<vector<int> > &matrix) {
        int m = matrix.size();
        if (!m) return;
        int n = matrix[0].size();
        int a00r, a00c;
        a00r = a00c = 1;
        // traverse the matrix
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                if (matrix[i][j] == 0) {
                    if (i == 0 || j == 0) {
                        if (!i) a00r = 0;
                        if (!j) a00c = 0;
                    } else {
                        matrix[0][j] = 0;
                        matrix[i][0] = 0;
                    }
                }
            }
        }
        // set row to 0
        for (int i = 1; i < m; i++) {
            if (matrix[i][0] == 0) {
                for (int j = 1; j < n; j++) {
                    matrix[i][j] = 0;
                }
            }
        }
        // set column to 0
        for (int j = 1; j < n; j++) {
            if (matrix[0][j] == 0) {
                for (int i = 1; i < m; i++) {
                    matrix[i][j] = 0;
                }
            }
        }
        // set first row to 0
        if (a00r == 0) {
            for (int j = 0; j < n; j++) matrix[0][j] = 0;
        }
        // set first column to 0
        if (a00c == 0) {
            for (int i = 0; i < m; i++) matrix[i][0] = 0;
        }
    }
};
